A type of network deployment has been introduced to a next generation wireless network, and in this type of network deployment, one base station has two cells of different frequencies, and a terminal may maintain connection to the two cells of different frequencies of one base station simultaneously. Of the cells that maintain connection to one terminal, one is a primary serving cell and the other is a secondary serving cell. FIG. 1 is a schematic signaling diagram of a network system. As shown in FIG. 1, communication between a terminal and a base station may be divided into the following several steps: first, the base station sends a random access resource allocation message to the terminal over a primary serving cell, where the message includes a serial number of a random access preamble code and a serial number of a physical random access channel (Physical Random Access Channel, hereinafter referred to as PRACH) mask code, and the message uses a cell radio network temporary identifier (Cell Radio Network Temporary Identifier, hereinafter referred to as C-RNTI) to scramble the random access resource allocation message; second, after using the C-RNTI to descramble the received random access resource allocation message, the terminal sends a random access request message to the base station over a secondary serving cell according to the random access resource allocation message received by the terminal, where the random access request message includes a random access preamble code; third, the base station sends a random access response message to the terminal over the primary serving cell according to the received random access request message, where the random access response message includes a time advance command TAC (Time Advance Command, hereinafter referred to as TAC); and finally, the terminal adjusts, according to the random access response message sent by the base station, time advance (Time Advance, hereinafter referred to as TA) of the terminal on the secondary serving cell.
In actual network deployment, the primary serving cell and the secondary serving cell may also belong to different base stations. A base station to which the primary serving cell belongs is referred to as a primary base station, and a base station to which the secondary serving cell belongs is referred to as a secondary base station. FIG. 2 is a schematic signaling diagram of a network system. As shown in FIG. 2, an overall communication process of the system is as follows: first, a primary base station sends a random access resource allocation message to a terminal; second, the terminal sends a random access request message to a secondary base station; and finally, the primary base station sends a random access response message to the terminal.
In a process of implementing the present invention, the finds that normal communication cannot be performed when the primary serving cell and the secondary serving cell are connected but a delay over the connection is relatively long and a capacity is relatively small, wherein the capacity is the maximum data transfer rate of backhaul link between primary cell and secondary cell, as specifically shown in FIG. 2. First, the secondary base station does not know content of a random access resource allocation message sent by the primary base station to the terminal is, and as a result, a random access request message cannot be correctly received. Second, the primary base station does not know when the secondary base station receives the random access request message sent by the terminal and cannot determine when to send a random access response message to the terminal. Third, because the primary base station does not know content of the random access request message sent by the terminal to the secondary base station, the primary base station cannot correctly send the random access response message to the terminal.